Week 5 Flashcards
Each RBC circulates the whole body in _______ (amount of time)
20 secs
1 RBC contains ________ molecules of Oxygen on it
1 billion molecules of Oxygen/RBC
Each RBC has ________ molecules of hemoglobin on it
640 million
Hemoglobin structure; Composed of….
Composed of 4 polypeptides (string of amino acids), each called a globin, 2 of them alpha-globins and 2 beta globins
Heme: each globin contains __ heme group(s), each composed of….
Each globin contains a heme group, composed of porphyrin in a circular formation with a single iron in the middle. It is the iron + heme that contains oxygen attracting properties.
All about heme and globin structure and function:
Heme is a metallo-porphyrin
contains iron atoms & red pigment porphyrin
binds respiratory gases (O2 & CO2) and other less beneficial substances
Globin is a protein
composed of 4 amino acid chains:
2 alpha chains & 2 beta chains
Heme + globin = Hemoglobin
chain conformation allows the heme to bind, transport & release gas molecules
a tetrameric hemeprotein
____ hemes + ____ globins = Hemoglobin
What are the two states of hemoglobin?
4 globins + 4 hemes = hemoglobin
2 states: oxyhemoglobin - oxygen bound (bright red)
deoxyhemoglobin - without oxygen (bluish-red)
Hemoglobin Variants
3 normal variants (no clinical manifestations):
–Hemoglobin A (97% of total cell hemoglobin)
•2 alpha chains, 2 beta chains
–Hemoglobin A2 (
Fetal Hemoglobin
Child – Hemoglobin F (fetal)
Newborn: 50-80%
6 months: 8%
>6 months: 1-2%
Good graph of hemoglobin production at all stages of life (within first 15 slides)
sldfkja
Hemoglobinopathies are members of a family of genetic disorders caused by:
Hemoglobinopathies are members of a family of genetic disorders caused by:
1- Production of a structurally abnormal hemoglobin molecule
(Qualitative hemoglobinopathies)
Or: 2- Synthesis of insufficient quantities of normal hemoglobin
(Quantitative hemoglobinopathies)
Or: 3- both (rare).
Thalessemia
2 main types:
A genetic blood disorder where the body makes reduced amounts of globin chains.
•2 main types:
–Alpha thalassemia
•Affects alpha globins (most common in SE Asia, Middle East, China, Africa)
–Beta thalassemia
•Affects beta globins (most common in Mediterranean origin)
Both types (___________ and __________) of thalessemia can occur in the major or minor forms.
Symptoms include:
Both types (alpha and beta) can occur in the major or minor forms
Children with beta thalassemia major (Cooley’s anemia) develop anemia during first year of life. Other symptoms include:
- Bone deformities in the face
- Fatigue
- Jaundice
- Growth failure
- Shortness of breath, SOB
Beta Thalessemia Major
Hgb A1:
Hgb A2:
Hgb F:
Hgb A1: 5-20%
Hgb A2: 2-3%
Hgb F: 65-100%
- Thalessemia major is more sever!
Which thalassemia is more common? What does it result in?
Beta thalassemia minor is most common form (one beta chain is affected)
•Results in mild microcytic hypochromic anemia otherwise no clinical symptoms
Abnormal (Clinically significant) hemoglobin variations: Hemoglobin S: Hemoglobin C: Hemoglobin E: Hemoglobin Constant Spring: Hemoglobin H: Hemoglobin Barts:
Hemoglobin S
–Predominant in people with sickle cell disease. Disease exists on beta chain.
•Hemoglobin C
–Disease is relatively benign with mild hemolytic anemia and splenomegaly
•Hemoglobin E
–Mild hemolytic anemia and splenomegaly. Extremely common in SE Asia
•Hemoglobin Constant Spring
– Alpha chain is abnormally long resulting in a thalassemic phenotype.
•Hemoglobin H
– Composed of 4 beta chains. Happens in extreme limitation of alpha chains.
•Hemoglobin Barts
– No alpha chains are produced. Most individuals die in utero
How can you differentiate and determine which hemoglobinopathies are present in any given blood sample?
Genetic testing
mass spectroscopy
-Gel electrophoresis
Inherited defects in globin structure mostly involve……
Inherited defects in globin structure mostly involve a single amino acid substitution
Why do cells sickle?
- Glutamic acid is substituted for valine
* Allowing the polymerization of sickle hemoglobin when deoxygenated
Normal vs. Sickle cells
Shape?
Pliability?
Lifespan?
Normal
•Disc-Shaped
•Deformable
•Life span of 120 days
Sickle
•Sickle-Shaped
•Rigid
•Lives for 20 days or less
Hemolysis and Vaso-occlusion
Hemolysis:
The anemia in SCD is caused by red cell destruction, or hemolysis, and the degree of anemia varies widely between patients. The production of red cells by the bone marrow increases dramatically, but is unable to keep pace with the destruction.
Vaso-occlusion:
Occurs when the rigid sickle shaped cells fail to move through the small blood vessels, blocking local blood flow to a microscopic region of tissue. Amplified many times, these episodes produce tissue hypoxia. The result is pain, and often damage to organs.
Sickle cell trait (heterozygous)
Hgb S:
Hgb A1:
Hgb A2:
Hgb F:
Incidence is about __% of African Americans
Hgb S: 20-40%
Hgb A1: 60-80%
Hgb A2: 2-3%
Hgb F: 2%
•Incidence is about 8% of African Americans
•No anemia or clinical evidence of disease
•May develop splenic infarcts under hypoxic conditions
-Some may develop hematuria
Sickle cell trait (Homozygous)
Hgb S:
Hgb A1:
Hgb A2:
Hgb F:
incidence in __% of african Americans
Hgb S: 80-100%
Hgb A1: 0%
Hgb A2: 2-3%
Hgb F: 2%
- Incidence is 6 months of age
- Anemia is moderate to severe with slight jaundice
- Significant number of patients die before age 40
- Sickle crisis may produce small infarcts in various organs, abdominal & bone pain most common
Hemoglobin C
Autosomal recessive disorder
•Similar to Hb S but glutamic acid to lysine substitution
•Considered a benign hemoglobinopathy
•Causes mild hemolytic anemia
•Unstable hemoglobin precipitates in RBCs and forms crystals
•Spleen removes defective RBCs from circulation
•Decreases the risk of malaria
Hemoglobin C disease (homozygous) Hgb C: Hgb A1: Hgb A2: Hgb F:
Incidence is about __% of African Americans
Hgb C: 90-100%
Hgb A1: 0%
Hgb A2: 2-3%
Hgb F: 2%
- Incidence is about 3% of African Americans from northern Africa
- Mild to moderate reduction in RBC lifespan
- Abdominal & bone pain occur, less severe than sickle disease
- Large number of target cells on blood smear (30-90%)
The Malaria Hypothesis
•When mapped out, the global distribution of malaria and populations with high carrier frequencies for hemoglobinopathies are essentially the same
•Being a carrier protects you from Malaria so you have an evolutionary “advantage” over a non-carrier.
•How does this work?
•Hasn’t been pinned down yet, but theories abound
Hb S – reduces oxygen tension in cells retarding growth of the parasite
•A thalassemia – confers susceptibility to a milder form of malaria; once contracted, the patient has immunity to the more severe form and increased survival
•B-thalassemia - ???; possibly a role in decreasing cell adhesions in the deadly cerebral form of malaria
Heme synthesis
___% of heme synthesis occurs in RBCs
85% of total heme synthesis occurs in red blood cells (RBC)
•Ceases when RBC’s mature
•Heme stimulates protein synthesis in reticulocytes
Heme synthesis in the liver
Heme produced in the liver is used mainly for the synthesis of …
The liver is the main non-RBC source of heme synthesis
•Heme produced in the liver is used mainly for the synthesis of the cytochrome P450 class of enzymes that are involved in detoxification
Porphoryias
The two cardinal symptoms in patients with porphyria are:
A group of disorders caused by deficiencies of enzymes of the heme biosynthetic pathway.
Two cardinal symptoms in patients with porphyria are photosensitivity and neurologic disturbances
•Acute porphyrias:
–Affect the nervous system. Signs and symptoms come on quickly and last a short time. Sx include: abdominal pain, vomiting, constipation, diarrhea. Sometimes seizures, anxiety and hallucinations can occur and the disease may be life threatening.
•Cutaneous porphyrias:
–affect the skin. Once exposed to sun, skin becomes fragile and blistered, leading to infection, changes in skin pigmentation and hirsutism
The porphyrias can also be defined by where the damaging compounds originate:
Bone marrow:
Hepatic:
Mixed:
Acquired:
They can also be defined by where the damaging compounds originate:
–Erythropoietic (bone marrow)
•Low number of RBCs , enlargement of the spleen
–Hepatic (liver)
•Abnormal liver function, increased risk of developing liver cancer
–Mixed
•Both hepatic and erythropoitic
–Aquired
•No genetic component, drug induced or due to lead poisoning
Lead poisoning
Lead inhibits bone marrow delta-aminolevulinic acid dehydratase (ALAD), a key enzyme in heme synthesis.
•Then the highly reactive oxyradical Delta-aminolevulinic acid (ALA) heme precursor accumulates, and is reported to cause liver cancer.
•Basophilic stippling in RBC’s
Lab testing for the porphyrias
Lab testing:
–Samples can be tested from blood, random or 24 hour urine, and/or a stool sample
–If acute or neurologic porphyria is suspected, a sample should be taken during an acute attack.
–Testing measures porphorins and their toxic precursors that have built up in tissue and fluids.
–Specialty labs may also measure for involved enzymes or genetic testing
Hgb, Hct, and RBC indices
All are interrelated RBC parameters
•In general, decreases in RBC leads to decreases in Hemoglobin & Hematocrit
•The relationship between these 3 parameters allows calculation of the RBC indices
•Be able to classify anemia based on the RBC indices & provide a possible etiology
Hemoglobin Measurements
Hemoglobin Measurements
•Most common method used to measure total hemoglobin content is spectrophotometric analysis.
•Based on the premise that substances absorb light energy at different wavelengths.
Spectophotometry for inspecting hemoglobin
RBCs are sent through a lyzing chamber. Membranes rupture releasing hemoglobin. Blue or green wavelengths are projected through the sample. The amount of light not absorbed is collected and analyzed (using beer’s law) to determine the hemeoglobin content within the sample.
Hemoglobin normal values:
Normal values
Males: 14.0-17.4 g/dL
Females: 12.0-16.0 g/dL
Children: 11.0-16.0 g/dl
Hemoglobin spectroscopy interfering factors:
Interfering factors: Very high WBC counts Severe lipidemia RBC abnormalities Increased turbidity Increased bilirubin
(many of these will absorb some of the light in the spectroscopy?)
Decreased levels of hemoglobin
Decreased levels: •Decreased RBCs – bone marrow defects –renal disease –cell destruction –blood loss •Hemoglobinopathies •Lead poisoning •Iron deficiency •Increased blood volume –Pregnancy –over-hydration
Increased levels of Hemoglobin:
Increased levels: •Increased RBCs – Polycythemia vera –renal tumors •COPD •Pulmonary fibrosis •Heart disease •Decreased blood volume –Dehydration
Hyperchromic
Hypochromasia: Morphology: Increase in the red cells' central pallor which occupies more than the normal third of the red cell diameter. Found in: - Iron deficiency -Thalassemia
Hematocrit
Definition:
The volume of erythrocytes expressed as a percentage of the volume of whole blood.
It is an indirect measurement of RBC number & volume since it is directly affected by these two parameter
Hct = Hgb x 3
The hematocrit is approximately 3X the hemoglobin value when RBCs are normal size and contain normal amounts of hemoglobin.
Hematocrit normal values
Normal values: Males: 42-52% Females: 36-46% Pregnant female: >33% Elderly: may be slightly decreased
Hematocrit incr. values
Increased values •Erythrocytosis •Congenital heart disease •Polycythemia vera (PCV) •Severe dehydration •Severe COPD
Decr. Values of hematocrit
Decreased values (anything that decr. RBC population OR anything that increases your plasma amount) •Anemia •Hemoglobinopathies •Cirrhosis •Hemolytic anemia •Hemorrhage •Nutrient deficiencies •Bone marrow failure Prosthetic valves •Renal disease •Normal Pg: 2nd trim. •Rheumatoid/collagen vascular diseases •Blood cancers and malignancies
Interfering factors with hematocrit levels
Interfering factors:
- RBC size has influence: larger RBCs associated with higher Hct because larger cells take up greater percentage of total volume
- Extremely high WBC counts falsely decrease
- Over and under hydration
- Pregnancy decreases due to hemodilution in 2nd trim.
- High altitudes increase due to hypoxia
- Post-hemorrhage values not reliable for several hours
- Drugs may decrease – chloramphenicol, penicillin
RBC indices
Red blood cell indices are measurements that describe the size and oxygen-carrying protein (hemoglobin) content of red blood cells.
•The relationships between the hematocrit, the hemoglobin level, and the RBC are converted to red blood cell indices through mathematical formulas.
•They are used to help in the differential diagnosis of anemia.
•These formulas were worked out and first applied to the classification of anemia’s by Maxwell Wintrobe in 1934
RBC indicies; Indications:
Indications:
The RBC indices provide valuable information regarding:
the size (MCV)
hemoglobin weight (MCH)
hemoglobin concentration (MCHC) of RBC’s
Useful information in classifying anemia
Mean Corpuscular Value
Mean corpuscular volume
Average volume of RBCs.
Reported as fL, femtoliters.
Derived from the RBC histogram by multiplying the # of RBCs by the size of the RBCs and multiplied by a calibration constant, or the mean of the red blood cell distribution histogram= MCV.
Normal: 82-97 fL
decreased MCV = microcytic RBCs (100 fL)
Interfering factors of MCV
Interfering factors:
–Anything that affects RBC counts or RDW:
•Very high WBC count
•High concentration of very large platelets
•Agglutinated RBCs
•RBC fragments that fall below the 36 fL threshold
MCH
Mean corpuscular hemoglobin
The average weight of Hgb in a RBC, reported in pg, picograms.
A calculated value.
Normal range: 26-34 pg of Hgb/RBC.
MCH = Hemoglobin x 10
# RBC in millions
MCH Values follow the MCV:
decreased MCH: small RBCs contain less Hgb
Increased MCH: large RBCs contain more Hgb
It’s basically a worthless value, it’s basically another measure of the size of a RBC, large RBC will have lots of room for Hgb and vice versa, so it will always follow MCV values
RBC indicies- MCHC
Mean corpuscular hemoglobin concentration
A “weight to volume” ratio of the average concentration of Hgb in a given volume of RBCs.
A Calculated value.
Reported as g/dL.
Normal MCHC = 32-36 g/dL
MCHC = Hgb (g/dL) x 100
Hct (%)
MCHC is used to help classify type of anemia
Normal MCHC = normochromic anemia
Decreased MCHC
You can’t put more hemoglobin in normal RBC’s, the only way to pack more in is to change the shape! so check blood for spherocytes in a smear
RBCs can NOT be
considered hyperchromic
•MCHC values have a
theoretical limit of 37; only 37 g/dl of hemoglobin can fit into an RBC!
•Automated machines may indicate MCHC >37 in those with spherocytosis, hyperlipidemia, cold agglutinins, & rouleaux formation
Anemias may be categorized according to RBC indices:
Anemias may be categorized according to RBC indices:
Normocytic = normal RBC size Microcytic = smaller than normal RBC size Macrocytic = larger than normal RBC size Normochromic = normal hemoglobin content Hypochromic = decreased hemoglobin content
Normocytic, Normochromic anemias could indicate:
Normocytic, normochromic anemias: •Chronic illness – the “anemia of chronic disease” (early stages) •Renal disease •Acute blood loss •Aplastic anemia •Acquired hemolytic anemia
Microcytic, hypochromic anemias indicate:
Microcytic, hypochromic anemias: •!Iron deficiency! due to: –Malabsorption –Malnutrition –Loss of blood (non-acute) •Sideroblastic •Lead poisoning •Anemia of chronic disease (later stages) •!Thalassemia!
Macrocytic, normochromic anemias indicate:
Macrocytic, normochromic anemias:
•!Vitamin B12! or folic acid deficiency
•Pernicious anemia
•Side effects of chemotherapy
•Myelodysplastic syndrome:
BM abnormalities that results in decreased production of RBCs & WBCs
often a precursor to development of Acute Myelogenous Leukemia (AML)
Each red cell has ___________ molecules of Hb
Each red cell has 640 million molecules of Hb
